 ;; **Task:**
 ;; Find the sum of all the primes below two million.
 
-(defn p010 [n]
+(defn p010 
+  ([] (p010 2000000))
+  ([n]
   (->>
    primes
    (take-while #(< % n))
-   (reduce +)))
-
-;; calculation
-;; (p010 2000000)+   (reduce +))))
;; - rec case: ``fib (n > 1) = fib(n - 1) + fib(n - 2)``

(defn p002
  "*Int -> Int*  
  Retrieve the sum of all even Fibonacci numbers up to n."
  ([] (p002 (* 4 1000 1000)))
  ([n]
   (->> fibs

;; Find the sum of all the multiples of 3 or 5 below 1000.

(defn p001
  ([] (p001 1000 3 5))
  ([limit & divisors]
    ;; for the range 0 to (limit - 1)
